Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
2000-03-09
2001-11-20
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
Reexamination Certificate
active
06318960
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a gas turbine stationary blade, and more particularly, to a gas turbine stationary blade structured such that the shape of the blade leading edge is improved so as to blow a blade cooling air with an enhanced efficiency, a thermal stress concentration is avoided and a blade assembling is facilitated.
2. Description of the Prior Art
FIG. 6
is a cross sectional view showing a representative first stage stationary blade of a prior art gas turbine. In
FIG. 6
, numeral
20
designates a first stage stationary blade, numeral
21
designates an outer shroud and numeral
22
designates an inner shroud. Numerals
20
a
,
20
b
,
20
c
,
20
d
,
20
e
designate cooling air holes, respectively, wherein the holes
20
a
are provided in the blade leading edge, the holes
20
b
in the blade trailing edge, the holes
20
c
in the blade leading edge portion, the holes
20
d
in the blade central portion and the holes
20
e
in the blade trailing edge portion. Within the stationary blade
20
, there are provided a passage
23
in the blade leading edge portion, a passage
24
in the blade central portion and a passage
29
in the blade trailing edge portion. An insert
25
is inserted into the passage
23
and an insert
26
is inserted into the passage
24
. The inserts
25
,
26
are provided in the passages
23
,
24
, respectively, with predetermined spaces being maintained from inner wall surfaces of the respective passages
23
,
24
and are supported at a multiplicity of points. Both of the inserts
25
,
26
are made in hollow cylindrical members and a multiplicity of air blowing holes
27
,
28
are bored in and around entire walls of the inserts
25
,
26
, respectively.
In the above mentioned first stage stationary blade, cooling air
30
,
31
,
32
is led into the stationary blade
20
from a turbine casing space (not shown) through the outer shroud
21
, wherein the cooling air
30
flows into the insert
25
on the leading edge side and then flows out of the air blowing holes
27
of the insert
25
into a space formed between an inner wall of the passage
23
and an outer wall of the insert
25
to effect an impingement cooling of the inner wall of the passage
23
. The cooling air
30
then flows out of the cooling air holes
20
c
bored in the blade and onto an outer surface of the blade to effect shower head cooling and film cooling of the blade outer surface.
The cooling air
31
likewise flows into the insert
26
and then flows out of the air blowing holes
28
of the insert
26
into a space formed between an inner wall of the passage
24
and an outer wall of the insert
26
to effect the impingement cooling of the inner wall of the passage
24
. The cooling air
31
then flows out of the cooling air holes
20
d
bored in the blade and onto the outer surface of the blade to effect film cooling of the blade outer surface. Also, the cooling air
32
flows into the passage
29
on the trailing edge side to cool a rear portion of the blade and flows out of the cooling air holes
20
e
of the blade trailing edge portion and onto the outer surface of the blade to effect film cooling thereof.
In the first stage stationary blade as described above, there occurs a non-uniformity of outflow air at the blade;s leading edge which causes an irregularity in the air flow velocity. This often results in an increased pressure loss or a back flow of the cooling air. There also occurs a clogging of the air blowing holes of the insert within the blade due to dust in the cooling air. This results in an increased pressure loss. Also, when the insert is to be assembled into the blade, there are a multiplicity of points to fix the insert in the air passage. Since the work space is narrow, assembling errors are more common and a lot of time is required for assembling the insert. Further, in terms of thermal stress, portions of the blade which are connected to the outer shroud and the inner shroud are structured so as to have only small fillet curves. As a result, thermal stress may concentrate in these areas and cause cracks. Thus, for a gas turbine that is operated at a higher temperatures, it is strongly desired to solve the above mentioned problems in order to enhance a reliability of the stationary blade.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a gas turbine stationary blade having an improved structure in which the air flows smoothly out of the blade's interior onto a curved surface of the blade's leading edge, film cooling holes through which the air flows out are prevented from clogging, inserts that are supported by simple supporting structures and fillet curves at the blade's connecting portions that are formed so as not to cause thermal stresses, thereby cooling efficiency of the blade is enhanced, assembly of the blade is facilitated and reliability of the stationary blade is improved.
In order to achieve the above objectives, the following (1) to (8) aspects of the present invention are provided hereinbelow:
(1) A gas turbine stationary blade is constructed of a blade that is fixed to an outer shroud and an inner shroud, wherein cooling air flows in the blade for cooling thereof. A projection is provided on a portion of a leading edge portion of the blade. The projection has a smooth curved surface as well as a plurality of cooling holes through which the cooling air is blown.
(2) A gas turbine stationary blade as mentioned above in the first aspect of the invention, characterized in that the projection has a curved surface formed as an elliptical curve on an ellipse long axis.
(3) A gas turbine stationary blade as mentioned above in the first aspect of the invention, characterized in that the projection is projecting from the leading edge of the blade.
(4) A gas turbine stationary blade as mentioned above in the first aspect of the invention, characterized in that the leading edge of the blade has a curved surface formed to an elliptical curve on an ellipse long axis.
(5) A gas turbine stationary blade constructed such that the blade is fixed to an outer shroud and an inner shroud, and a plurality of passages are provided in the blade. Each of the passages receives a cylindrical insert, which includes a multiplicity of air blowing holes, to be fixed therein with a predetermined space maintained from an inner wall of each of the passages. The air blowing holes of the insert provided on a leading edge side of the blade include a first group and a second group. Each hole of the first group has a diameter larger than that of each hole of the second group. The first group of the air blowing holes is provided in a dorsal side rear portion of the insert. Also, a plurality of cooling holes, each of which has a diameter that is larger than other cooling holes in the blade, are provided in a dorsal portion of the blade near the first group of air blowing holes formed in the insert.
(6) A gas turbine stationary blade as mentioned above in the fifth aspect of the invention, characterized in that the insert in each of the passages is supported at two places.
(7) A gas turbine stationary blade as mentioned above in any one of the six aspects of the present invention, characterized in that fillets connect portions of the blade to the outer shroud and the inner shroud have curved surfaces formed as an elliptical curve on an ellipse short axis.
(8) A gas turbine stationary blade constructed such that a blade is fixed to an outer shroud and an inner shroud, and a plurality of passages are provided in the blade. Each of the passages receives a cylindrical insert, which includes a multiplicity of air blowing holes, to be fixed therein with a predetermined space maintained from an inner wall of each of the passages. A leading edge of the blade has a curved surface formed on an elliptical curve on a major axis of the ellipse. A projection formed at the leading edge portion of the blade and is located on the camber line of the blade. The project
Ito Eisaku
Kuwabara Masamitsu
Tomita Yasuoki
Mitsubishi Heavy Industries Ltd.
Ryznic John E.
Wenderoth , Lind & Ponack, L.L.P.
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